Version is Alpha 7 (184.108.40.206), on Windows 11 using a Wacom Intuos Pro. The keyboard shortcuts for each of Jump to Start, Step Backward, Play, Step Forward, and Jump to End all work, and each of them work with the Wacom pen too. However, the last three do not work with the mouse.
Expected outcome would be consistency across hotkeys, wacom tablet and mouse interaction. Interesting that it is only the last three that do not work for the mouse.